It is a well known problem that use of shaped charged perforators in oil and gas wells produces formation damage by the generation of high energy particulated metal jet of energy which tends to block the pores in the earth's formations. It is also recognized that "back surging" methods which involve creating a high differential pressure across the perforations and subsequent quick release of the pressure differential can induce a release of the damaged surface areas and larger volume flows can be obtained so that the well production is increased.
Prior systems for back surging of perforations in a casing usually have one or more of the following undesirable features:
1. The well may have to be killed, the packer unseated and the production tubing pulled. This means a substantial loss of time and considerable expense as well as possible permanent damage to the well.
2. A safety hazard may exist by running dry production tubing into the well with a rupture type bottom closure in the tubing. This type of back surging system involves a dry production tubing with a frangible bottom closure and it is possible to lose pressure control during the operation.
3. The back surging systems may leave undesirable parts and debris in the bottom of the well which subsequently may affect the production from the well.
The present invention contemplates apparatus and methods to back surge perforated oil and gas wells which have a high differential pressure and high volume flow and will eliminate the above listed undesirable features.
The applicant has a prior U.S. Pat. No. 4,142,583 which is directed to a different type of back pressure apparatus system.